1. Field of the Invention
The present invention relates to a synthetic board and a method of producing the same.
2. Description of the Related Art
A synthetic board used for an interior member of a vehicle, a building component and the like includes woody material, such as woodchips and wood fibers, and an adhesive for binding the woody material. The method of producing a synthetic board of this type has the step of mixing the woody materials with an adhesive and the step of molding an obtained mixture.
As an adhesive for a synthetic board, a phenol resin or the like has conventionally been used. However, when a synthetic board containing an oil-derived synthetic resin is burnt, there generates carbon dioxide, and this increases the amount of carbon dioxide in the earth's atmosphere. In addition, the phenol resin contains free phenol and formaldehyde, which have the possibility to make negative effects on the human body.
Given this situation, the method of producing a synthetic board that is free of an oil-derived synthetic resin has been developed. According to the method of producing a synthetic board, which is disclosed in Unexamined Japanese Patent Application Publication No. 2001-1318, lignocellulosic material is subjected to steam treatment. The steam-treated lignocellulosic material is heat-pressed, and is then molded into a synthetic board. In this producing method, hemicellulose that is a component of lignocellulose is hydrolyzed by the steam treatment, and the lignocellulosic material is bound through the hydrolysate of the hemicellulose.
Being made of plant-derived materials alone, the synthetic board disclosed in the above document is environmentally friendly. That is to say, the amount of the carbon dioxide that is discharged when the synthetic board is burnt and the amount of the carbon dioxide that is absorbed when the plants grow set off each other. Therefore, this synthetic board does not increase the amount of carbon dioxide in the earth's atmosphere. In addition, the synthetic board scarcely contains substances that have effects on the human body.
The producing method described in the above publication, however, requires heat press to be carried out at high temperature and pressure for long hours as compared to the case in which an oil-derived synthetic resin is mixed as an adhesive. There also is the problem that the synthetic board thus obtained is inferior in strength to the synthetic board produced by mixing the oil-derived synthetic resin, and is inadequate for the use as an interior member of a vehicle or a building component.
The synthetic board that has recently been developed contains as an adhesive a plant-derived resin such as polylactic acid resin instead of an oil-derived synthetic resin. However, the polylactic acid resin is inferior in flexibility and is brittle. Moreover, the polylactic acid resin is also hard to handle as it is hydrolyzed or biodegraded during use.
Unexamined Japanese Patent Application Publication No. H09-39127 discloses a fabric covered synthetic board as an interior material. The fabric covered synthetic board includes a synthetic board and a woven or nonwoven fabric laminated onto the surface of the board. The step of laminating the fabric onto the synthetic board includes the application of an adhesive to the surface of the synthetic board, disposition of the fabric on the surface, and a process of pressing the fabric and the synthetic board. Such a step incurs an increase in manufacturing cost of fabric covered synthetic boards because of the use of the adhesive, addition of the pressing process, etc. In this step, a solvent adhesive or the like is generally used as an adhesive. The solvent adhesive contains, for example, chloroprene rubber as an adhesive component, and also contains as solvent an organic solvent, such as acetone, toluene and n-hexane. A large quantity of organic solvent has the possibility to make negative effects on the human body, so that the content of the organic solvent must be controlled when the organic solvent is contained in the fabric covered synthetic boards to be used for vehicles and buildings.